The present invention relates generally to bearings, and more particularly to a dual-mode twin-chamber thrust bearing having hydraulic damping.
A dual-mode twin-chamber thrust bearing having hydraulic damping in particularly suited for use as an engine bearing in motor vehicles. The bearing has a working chamber and an equalizing chamber which are separated by a partition. The partition is provided with a passageway that can be closed by an actuator, and also has a damping channel that hydraulically links the two chambers. A membrane is located in a recess in the partition. The membrane effectively covers openings in the partition on both sides and can be sealingly positioned by the actuator.
Bearings of this type are used to damp both high-frequency, low-amplitude and low-frequency, high-amplitude vibrations. Higher-frequency vibrations that occur during vehicle operation are isolated by the membrane, which is arranged in a nozzle cage and becomes effective when the passageway in the center of the partition is closed. Low-frequency vibrations are suppressed by the damping channel. For example, in order to suppress low-frequency vibrations during idling, the passageway in the partition is opened and the liquid column present in the passageway acts as a damper for the vibrations.
U.S. Pat. No. 5,344,127, which is incorporated by reference, describes a dual-mode twin-chamber thrust bearing where the passageway located in the center of the partition can be closed using an actuator. The actuator is actuated by vacuum and keeps the passageway closed during operation, but the passageway is opened during idling. This embodiment has proven useful in many applications.
German Patent Application 198 07 868 represents an improvement with respect to the above-mentioned embodiment. In that patent, damping of vibrations caused by idling and isolation of higher-frequency vibrations in a speed range above idling speed is improved by the fact that the membrane can be sealingly positioned by the actuator when the passageway in the partition is opened. During operation of an engine above idling speed, the passageway is closed by the actuator during operation above the idling speed, and the seal created by the membrane positioned within the partition is removed by a restoring spring in the actuator. In this operating state, the bearing functions as a generally known hydraulically damping bearing, where the membrane is arranged so that it can move loosely back and forth within the partition in order to isolate high-frequency, low-amplitude vibrations induced by the engine. In order to damp low-frequency, high-amplitude engine vibrations during idling, the passageway is opened and the liquid present in the passageway vibrates back and forth with a phase shift. This reduces the rigidity of the bearing if there are idling vibrations.
Consistently outstanding results are achieved by using the dual-mode membrane. An elastically pre-tensioned tension element secures the position of the membrane when the passageway is open. As soon as the passageway is closed by the actuator, the membrane is released. To accomplish this, the adjusting spring has to overcome both the force required for closing the passageway and force of the tensioning element.